1. Field of the Invention
The invention relates to an Automatic Document Feeder (ADF) having a sleeve, which is rotatably mounted on a rotating shaft and has a second engaging structure which is engaged with and disengaged from a first engaging structure disposed on a housing such that a replaceable friction roller assembly of the ADF may be easily replaced by a user.
2. Description of the Related Art
A friction roller assembly on an ADF of a conventional scanner is a consumptive part, for it is depleted through transporting sheets, so the friction roller assembly has to be replaced after being used for a period of time, such that the sheet transporting quality may be maintained. However, a rotating shaft of the friction roller assembly is usually fixed to a back plate of the ADF using a fixing element such as a C-ring, which cannot be easily removed by users. So, the users cannot replace the friction roller assembly.
U.S. Pat. No. 6,488,276 discloses a paper feeding device having a replaceable paper conveying roller, wherein a rotating shaft is fit into an open shaft hole in conjunction with associated engaging structures such that the users can easily disassemble and replace the friction roller assembly. FIG. 5 is a schematic illustration showing the prior art ADF having a replaceable friction roller assembly. As shown in FIG. 5, a friction roller assembly 120 has a rotating shaft 122 and a friction roller 124, and the rotating shaft 122 is fit into a closed shaft hole 112 and an open shaft hole 114 of a back plate 110. A pressing element 116 is provided to rotatably mount the rotating shaft 122 into the open shaft hole 114.
In the '276 patent, however, directly mounting the rotating shaft into the open shaft hole in conjunction with the engaging operation of the engaging structure produces an additional radial force exerting on the rotating shaft to increase the friction force between the shaft hole and the rotating shaft. If only one open shaft hole for accommodating one end of the rotating shaft is formed at one side of the back plate, the rotating shaft may be slantingly biased, and the sheet transporting procedure cannot be performed smoothly.